Bridge plug with compound by-pass valve



April 18, 1967 B. SCOTT BRIDGE PLUG WITH COMPOUND BY-PASS VALVE F iled Dec.

. 5 Sheets-Sheet 1 INVENTOR. 4%.! 5 56677 April 18, 1967 Filed Dec.

L. B. SCOTT BRIDGE PLUG WITH COMPOUND BY-PASS VALVE "-i iii 3 Sheets-Sheet 5 INVENTOR. 6 66 5. SCdfi' BY A! J@ United States Patent )filice a 3314,486 Patented Apr. 18, 1967 3,314,480 BRIDGE PLUG WITH COMPGUND BY-PASS VALVE Lyle B. Scott, South Gate, Califi, assignor to Byron Jackson Inc., Long Beach, Calif., a corporation of Delaware Filed Dec. 3, 1964, Ser. No. 415,645 12 Claims. (Cl. 166--121) The present invention relates to bridge plugs and more particularly to a so-called retrievable bridge plug having multiple by-pass valve means.

Bridge plugs are forms of well packers adapted to be run into a well on a wire line or on pipe and set or anchored in the well bore or casing to facilitate certain treatments of subsurface earth formations traversed by the well bore, the bridge plug forming a seal bridging the well bore whereby fluids may be injected into the Well and displaced therefrom in the earth formation which communicates with the well above the bridge plug. At other times, such packers or bridge plugs may be employed to hold subsurface pressure within the well below the packer.

In the use of such bridge plugs, it is necessary that they be lowered through existing fluids in the well bore and such fluids must pass through the body of the plug. Characteristically, the body of a bridge plug is provided with valve means that are operable when the plug is set to prevent flow through the plug body in either direction. However, when it is desired that the plug be released for recovery or movement to another location, such valve means must be opened against the existing fluid pressure. In the case, for example, when the plug is set beneath a substantial column of well fluid, there is a force of thousands of pounds acting to hold the valve means closed and the packer set. In some instances, the pipe string with which the plug may be retrieved may have inadequate tensile strength to overcome thousands of feet of hydrostatic pressure applied to the responsive 'area of the valve, particularly in larger diameter plugs. In other instances, the pipe string may be so stretched that violent reactions are experienced as a consequence of sudden opening of the valve means and release of the tension loading on the pipe on the order of many thousands of pounds.

In accordance with an object of the present invention, valve means are provided which open under substantially less force. i.e., the force holding the valve means closed is small as compared with conventional plugs of the same size. As a consequence of the improved valve means, moreover, a valve means which has an overall larger diameter than comparable size conventional plugs and therefore the diameter or flow area of the by-pass passage through the plug body may be correspondingly larger, thus facilitating the running and retrieval of the tool through liquid filled well bores.

In accordance with the foregoing, it is a more specific object to provide a bridge plug having a first valve means of a small area which will respond to opening forces applied by the inner actuating rod of the plug and which will open to allow balancing of pressure across a larger second valve means which will also be opened by forces applied to the inner rod of the plug.

Still more specifically, the invention contemplates the provision of compound valve means including a pair of concentric valve heads mounted one on the other and openable sequentially upon opening movement of the inner rod of the plug, one of the valves being small and offering only a small pressure responsive area subjected to the pressure of fluid tending to hold the valve closed, so that the small area valve will be opened to allow balancing of the differential pressure across the compound valve, so that the larger valve will easily be opened.

Other objects and advantages of the invention will be hereinafter described or will become apparent to those skilled in the art, and the novel features of the invention will be defined in the appended claims.

In the accompanying drawings:

FIGS. 1 and 1a are longitudinal sectional views through the upper and lower part, respectively, of a bridge plug made in accordance with the invention, in condition for running into a well bore;

FIGS. 2 and 2a are views corresponding to FIGS. 1 and la, with the plug shown set in a well bore;

FIG. 3 is 'a fragmentary longitudinal sectional view through the lower part of the assembly, as taken on the line 3-3 of FIG. la;

FIG. 4 is a transverse sectional view as taken on the line 44 of FIG. la;

FIG. 5 is a transverse sectional view as taken on the line 55 of FIG. 1a;

FIG. 6 is 'a transverse sectional view as taken on the line 7-7 of FIG. 2; and

FIG. 7 is a fragmentary longitudinal sectional view showing the compound valve means hereof initially opening against fluid pressure from above which is holding the plug in a set condition.

Like reference characters in the several views of the drawings and in the following description designate corresponding parts.

Referring to FIGS. 1 and In, it will be seen that the retrievable bridge plug of the present invention comprises an elongated inner member 1 threadedly connected as at 2 to an upper control :head generally designated 3. Disposed about the inner member 1 is an outer member in the form of a tubular assembly generally denoted at 4 and having in axially spaced relation thereon well wall-engaging anchor means generally denoted at 5 and located at the lower end of the tool, well wall-engaging friction means generally denoted at 6, and well wall-engaging packing means generally denoted at 7. At the lower extremity of the outer member 4 is a bottom cap or bullnose 8 suitably secured in the open lower end of the outer member 4.

The outer tubular member or assembly 4 consists of a lower tubular body 9 to the lower end of which is connected the nose 8, and adjacent the up er end of which is slidably disposed a drag block cage or carrier 10 having a central opening 11 through which the body 9 extends. The cage 1% is provided with a plurality of longitudinally extended, radial slots or grooves 12 which receive a like number of radially shiftable drag blocks 13 each having outer friction surfaces 14 engageable with the well casing. The drag blocks 13 are biased into frictional engagement with the well casing by spring means which, in the illustrative example, includes a plurality of coil springs 15 acting outwardly on the drag blocks and seating against the base of the drag block-receiving slots 12. Outward movement of the drag blocks 13 is limited by retainer rings 16 and 17 respectively located at the upper and lower ends of the drag block cage and secured thereon by means of fasteners 18 and 19, respectively.

At the lower end of the drag block cage 10, it is provided with downwardly opening slots 20 at a plurality of circumferentially-spaced locations in which is supported by means of pivot pins 21 a plurality of links 22 having at their respective upper extremities a tongue 23 engaged by a coiled compression spring 24, the latter seating in an opening 25 formed in the drag block carrier 10 against a downward extension 26 of the latter.

The outer extremities or lower ends of the links 22 are pivoted by pins 27 to the Well bore Wall-engaging anchor means 5 and, more particularly, it will be noted that the links 22 are each connected to a slip assembly designated 28 comprising a head 29 having arcuate wickered sections 30. Between the wickered sections 30, there is suitably affixed as by welding to each head 29, a connector bar 31 which extends longitudinally of the outer tubular member and is connected to a base slip member 32 between arcuate wickered sections 33 of the latter, as by suitable welds or the like, whereby the wicker sections and 33 of the slip assemblies 28 are unitized and movable as a unit about the pivot pins 27 of the respective links 22.

It will now be observed that the eifect of the coil spring 24 acting on the tongue 23 of the links 22 is to swing the lower ends of the links 22 inwardly so that the slip heads 29 abut with the outer tubular member 4, and in addition, the lower extremities of the links 22 are formed with abutment surfaces 34 which contact the slip heads 29 to prevent relative outward pivotal movement of the unitized slip assemblies about the pivot pins 27 while the links 22 are provided with a bevelled surface 35 which will permit outward pivotal movement of the links with consequent outward movement of the slip assemblies 28. Preferably, the lower ends of the slip assemblies 28 are confined and normally held in close proximity to the outer member 4 by means of a garter spring or rubber O-ring 36 which mutually embraces the base elements 32 of the slips 33 to hold the slip units in the positions shown in FIGURE 1.

Intermediate the wickered sections 30 and 33 of the slip assemblies and suitably formed on or made a part of the outer tubular member 4 is a double cone member generally denoted at 37 and having oppositely inclined conical faces 38 and 39, the conical face 38 being engageable with the wickered sections 30 of the slip assemblies and the conical face 39 being engageable with the wickered sections 33 of the slip assemblies whereby the respective wickered sections will be forced radially or laterally into anchoring engagement with the well wall responsive to relative longitudinal movement of the tubular member 4 in one direction or the other through the drag block carrier 10, the drag blocks 13 resisting movement of the slip elements along with the cone 37.

At its upper extremity, the body 9 of the outer tubular member 4 is connected as by a thread 49 to the base 58 of the valve body generally denoted 51. The base 56 has at its upper end a cup-like section 52 which flares outwardly and is longitudinally slotted at 53 at a plurality of circumferential locations to provide flow passages therethrough. Threaded as at 54 to, or otherwise made a part of the cup-like member 52, is a tubular packer support 55, to the upper end of which is connected as by a thread 56, or the like, an inverted cup-like member 57 provided with a plurality of circumferentially spaced slots 58 providing flow passages which communicate through the packer support 55 with thepassages 33. This cup-like member 57 is formed at the lower end of an upwardly extended valve body 59.

Mounted about the packer support 55 is a pair of opposed packer cups respectively designated 61 and 62. The cup 61 has a lip portion 63 extended upwardly for engagement with the well wall, while the cup 62 has a lip 64 extended downwardly for engagement with the Well wall, the lips 63 and 64 being spaced from the cup-like members 52 and 57 within the zone of the slots 53 and 58. The cup 61 is in abutment at its inner end with a gauge ring 65 disposed about the packer support 55, and the cup 62 likewise is in abutment at its inner end with a gauge ring 66, the gauge ring 65 having at its inner margin a seat 67 opposed to a similar seat 68 in gauge ring 66 for engagement with a split retainer ring 69 adapted to lit in an annular groove 70 extended about the packer support 55. This ring 69 holds the respective packer cups against longitudinal movement on the support 55.

Sealing means are also preferably provided to prevent leakage of fluid between the cups and their support 55; and such sealing means preferably includes a pair of O-rings 72 and 73 seating in grooves extended about the packer support 55 and engaged with the inner periphery of gauge rings 65 and 66.

Extended longitudinally through the outer tubular member 4 described above, is the elongated inner member generally denoted at 1. This inner member is a control member for use in the running and setting, as well as in the release and recovery of the well tool. The upper section of the control member 1 extends through the portion 59 of the outer member, through the packer support 55, through the base 50 of the cup-like member 52, and into the body 9.

Slidably disposed on the inner member 1 within the cup-like members 52 and 57 of the outer tubular assembly 4, are compound valve means including assemblies generally denoted at and 81, respectively. Each compound valve assembly comprises first valve means including annular heads designated 80a and 81a slidably disposed on inner member 1 and having a skirt 80b and 81b extending axially of the member 1 on which spider supports 80c and tile of a second valve means including a larger head 80d and 81d is slidably supported. The first valve means 80a and 81a are of comparatively small diameter or area and are adapted to sealingly engage in seats 80c and 816 circumscribing central opening-s through the respective second valve means 80d and 81d; while the latter are en-gageable with seats 82 and 83, respectively, formed on packer support or body section 55 at opposite ends thereof.

Compound valve 81 is adapted to prevent upward flow of fluid through body section 55, and hence spring means in the form of a coiled spring 84 acts upwardly on valve skirt 8% to move the head 80a upwardly relative to packer support or body section 55 towards seat 82. A coiled spring 84a engages valve head 80a and spider 30c which supports head 80d so as to normally bias the heads 80a and 8% into contact. Similarly, compound valve means 81 is provided with a coiled spring 85 which acts downwardly on skirt 81b to bias the valve head 81a towards seat 83 at the upper end of packer support or body section 55; while a coiled spring 85a engages head 81a and spider 810 to relatively longitudinally bias the heads 81a and 81d towards coengaging positions.

Compound valve means 30 is adapted to be unseated or opened by a flange 86 on the inner member 1, while compound valve means 81 is adapted to be unseated or opened by a flange 87 on the inner member 1. These flanges 86 and 87 are spaced longitudinally of the inner member 1 so that upon engagement of one of the flanges with one of the compound valve means and opening of the latter, say, for example, engagement of flange 8'6 with valve means 80 as shown in FIG. 1, the other flange is spaced from its compound valve means so that the latter is free to close under the influence of the coiled springs acting on the compound valve means, but the flow of fluid through the valve means which is held open by the inner member may force the other compound valve means off of its seat. Hence, with the inner member 1 in the position shown in FIG. 1, the respective valve means will allow the passage of well fluids upwardly through the body 55. However, were the inner member 1 positioned so that the upper compound valve means 81 were held open, the lower compound valve means 80 would be opened by fluid passing downwardly through body 55. Therefore, it will be understood that communication through the packer support or body section 55 between passages 53 and 48, that is, the ability of fluid to by-pass the packer assembly, is controlled by the valves 80 and 81 responsive to the positioning of the inner member 1 within the outer assembly 4.

As best seen in FIG. 3, the inner member 1 :at its lower extremity has a connector head 90 provided with an elongated slot 91. Extending transversely through the slot 91 is a crosshead 92, this crosshead extending diametrically of the tool through elongated slots 93 in the outer body 9 and being connected to the drag block cage or carrier 10. Hence, there is an efiective lost-motion connection between the inner control member 1 and the drag block carrier which will permit movement of the control member 1 longitudinally a distance sufiicient to allow the respective valve operating flanges 86 and 87 to contact and unseat the respective valves 80 and 81 upon longitudinal movement of the inner control member 1 without alIecting the longitudinal relationship between the body 9 of the outer tubular assembly and the drag block carrier 10.

Downward movement of the control member 1 within the outer tubular assembly 4 when the latter are in a normal angular relationship is prevented by abutment of the control head 3 with the upper extremity of the outer member 59. More particularly, in reference to FIG. 1, it will be noted that the member 59 is provided with a pair of elongated slots 95, and the control head 3 is provided with fingers 96 extending into the slots 95. Extended circumferentially between the fingers 96, the control head is provided with an abutment sunface 97 engageable with the end surface 98 of the outer member 59. The distance from abutment surface 97 to the upper extremity of the lost-motion slot 91 in the connector head 90 determines the relative longitudinal relationship between the body 9 of the outer tubular assembly 4 and a drag block carrier 10 and, there-fore, determines the relative longitudinal relationship between the cone 34 and the slip elements 30 and 33 of the slip assemblies 28.

Therefore, as seen in FIGS. 1 and 3, when the tool is being run into a well by weight applied to the control head 3, the contacting abutment surfaces 97 and 98 will cause the outer tubular assembly 4 to move downwardly along with the control member 1; and the crosshead 92 engaged at the upper end of the slot 91 with the connector head 90 will cause similar and simultaneous movement the drag block and the slip assembly along with the outer tubular assembly 4.

However, when running-in weight is relieved from the control head 3, the force of compression spring 84 acting upwardly on valve assembly 80 will move the latter into a closed position on its seat 82 and will thereby slightly raise the inner control member 86. Such upward movement of the control member 1 will move the connector head 90 upwardly relative to the crosshead 92 and thus the tool will be conditioned so as to be subsequently set or anchored in the well casing upon the application of fluid pressure from above against the packer cup 61 and the normally closed valve means 81 or pressure from below against cup 62 and the normally closed valve means 80.

In the event that pressure is applied from above, as during the injection of fluid into subsurface earth formations above the location at which the packer is set, then fluid pressure will, as shown in FIGS. 2-2a, cause downward movement of the outer tubular assembly 4 relative to the drag block carrier 10,the drag blocks of which are frictionally engaged within the well casing; thus downward movement of the tubular assembly 4 will cause downward movement of the tubular body 9 and the cone 37 carried thereby relative to the slip assemblies 28, with the result that the expander cone surface 39 will engage the wickered segments 33 to force the same into anchoring engagement with the well casing, so that the entire tool assembly will be held against downward movement. Conversely, when pressure is applied from beneath the tool, the tubular assembly 4 will be caused to move upwardly relative to the drag block carrier 10 and the expander surface 38 will engage beneath the wickered segments 30 to cause the latter to engage the well casing and hold the entire tool assembly against upward movement.

The control head 3 is adapted to accommodate a running and retrieving tool which may be connected to a wire line or to a length of pipe, as may be desired. Accordingly, the head is herein illustrated as having at its upper end a pair of diametrically extended pins 99 adapted to be engaged in a setting and retrieving head (not shown) having appropriate bayonet-slot type means for receiving the pins 99.

In addition, means are provided for normally maintaining the inner control member 1 oriented relative to the outer tubular assembly 4 in such a position that the fingers 96 on the control head will be longitudinally aligned with the grooves in the upper end of the outer tubular assembly. In the illustrative embodiment, this means includes an elongated torsion spring bar 100 which extends longitudinally in a bore 101 in the inner member 1 and is fixedly connected at its lower end by a coupling 192 to the inner member 1, and which is fixedly connected at its other end by a coupling 103 to the control head 3.

In order to test-set the tool when it is run into a well, the upper end of the member 59 of the outer tubular assembly 4 at one side of each of the slots 95 is provided with a circumferentially extended shoulder 104 engageable by the inner or lower end of the fingers 96 when the control member 1 is moved upwardly within the outer tubular assembly 4 and rotated, for example, one-quarter turn. In this connection, it will be understood that such upward movement of the inner control member 1 relative to the outer tubular assembly 4 is permitted by the elongated lost-motion connection slot 91. When the control head is rotated and engaged with the shoulders 104 following upward movement of the inner control member, subsequently applied downward load on the control head will be transmitted to the outer tubular body 4 without causing corresponding downward movement of the crosshead 92. Such downward movement of the body relative to the crosshead 92, and therefore relative to the drag block carrier 10, will cause the expander cone surface 39 to engage the wickered slip segments 33 to anchor the tool against downward movement, thus supporting the weight of the running-in string of pipe or wire line and indicating at the earths surface that the tool is in operating condition. Such test-setting must be effected while the control head is held under torque, tending to rotate the fingers 96 to a position at which they are angularly displaced from the slots 95; and, when such torque is released, the torsion spring bar 100 will return the fingers to their normal position in alignment with the slots.

When the tool is pressure set in the bore hole, and it is desired to release the tool to move it elsewhere in the hole or recover the tool, the inner member 1 is moved longitudinally, say upward in order to release a tool which is set and is sustaining a large pressure differential as a result of hydrostatic pressure of a column of fluid thereabove. In the present construction the pressure holding valve means 80 closed causes a much smaller force holding head 81a seated on head 81d than the total force holding both head 81a seated and head 81d seated. Therefore, referring to FIG. 7, it will be seen that flange 86 acts on the smaller valve head 31a to unseat the same in the initial stage of upward movement of inner member 1. Such initial opening of valve 81a allows the pressure to be balanced across the valve to enable ease of opening of the compound valve assembly 81.

As one consequence of the ease of opening of the compound valve assemblies, less strain is imposed on the inner rod and on the retrieving pipe or line. Hence, less stretching of the pipe or line occurs and the reaction experienced upon opening of ordinary prior valves is avoided.

While the specific details of the invention have been herein shown and described, changes and alterations may be resorted to without departing from the spirit of the invention as defined in the appended claims.

I claim:

1. In a retrievable bridge plug, comprising: an elongated tubular body having thereon well wall engaging packer means for forming a seal with the well wall, well wall engaging anchor means operable for anchoring said body to said well wall, well wall engaging friction means for effecting operation of said anchor means upon the application of pressure differential across said packer means, said body having a passage therethrough, an inner member extending longitudinally in said passage and having means for controlling operation of said anchor means,

said body having a valve seat, valve means carried by said inner member closable against said seat responsive to fluid pressure to prevent flow of fluid through said passage and openable upon movement of said inner member in said body, the improvement wherein said valve means comprises first valve means having a small area responsive to fluid pressure holding the same closed and openable responsive to initial movement of said inner member, and second valve means engageable with said seat and having a larger area responsive to fiuid pressure holding the same closed and openable responsive to further movement of said inner member.

2. A bridge plug as defined in claim 1, wherein said first and second valve means are concentrically disposed about said inner member, said second valve means having an opening closable by said first valve means responsive to fluid pressure.

3. A bridge plug as defined in claim 1, wherein said first and second valve means are concentrically disposed about said inner member, said second valve means having a central opening and a seat circumscribing said opening, said first valve means having a head engageable with said seat on said second valve means.

4. A bridge plug as defined in claim 1, wherein said first and second valve means are concentrically disposed about said inner member, said second valve means having an opening ciosable by said first valve means responsive to fluid pressure, and said first and second valve means having coengageable means for opening said second valve means upon such further movement of said inner member.

5. A bridge plug as defined in claim 1, wherein said first valve means includes a valve head slidably disposed on said inner member, said second valve means including a valve head also sli-dably disposed on said inner member and having a central opening, a valve seat circumscribin-g said central opening and engageable by said valve head of said first valve means, means biasing said valve heads toward their seats.

6. A bridge plug as defined in claim 5, wherein said head of said first valve means has a skirt slidable on said inner member and the said head of said second valve means has means slidable on said skirt.

7. A bridge plug as defined in claim 5, wherein said head of said first valve means has a skirt slidable on said inner member and the said head of said second valve means has means slidable on said skirt, and said means biasing said valve heads toward their seats includes a spring acting on said first valve means and on said body to urge said head on said first valve means into engagement with the seat on said second valve means.

- 8. A bridge plug, comprising: an elongated tubular body having a central flow passage therethrough and having thereon well wall engaging anchor means and packer means for sealing engagement with the well wall and for actuating said anchor means responsive to fluid pressure differential across said packer means, said packer means being operable to seal against flow in either direction past the outside of said body, an inner member disposed in said body and movable longitudinally therein, said body having opposing valve seats spaced longitudinally of said body, a pair of compound valve means carried by said inner member in spaced relation thereon and respectively engageable with said seats to prevent the flow of fiui-d through said body flow passage when said inner member is in one position in said body, and each of said compound valve means including a first valve means openable by said inner member upon initial movement of said inner member toward another position in said body and second valve means movable off of the respective valve seat upon further movement of said inner member toward said another position.

'9. A bridge plug as defined in claim 8, wherein said inner member includes spaced abutments located between said compound valve means, said abutments being re spectively engageable with said first valve means of said compound valve means upon said initial movement of said inner member in one direction longitudinally of said body.

10. A bridge plug as defined in claim 8, wherein said inner member includes spaced abutments located between said compound valve means, said abutments being respectively eng-ageable with said first valve means of said compound valve means upon said initial movement of said inner member in one direction longitudinally of said body, and including means on the first and second valve means of the respective compound valve means engageable following said initial movement of said inner member too open said second valve means upon further movement of said inner member in said one direction.

11. A bridge plug as defined in claim 8, wherein said inner member includes spaced abutments located between said compound valve means, said abutments being respectively engageable with said first valve means of said compound valve means upon said initial movement of said inner member in one direction longitudinally of said body, and including coengageable means on said body and said inner member for causing longitudinal movement of said body and inner member together following such further movement of said inner member in said one direction.

12. A bridge plug as defined in claim 8, wherein said inner member includes spaced abutments located between said compound valve means, said abutments being respectively engageable with said first valve means of said compound valve means upon said initial movement of said inner member in one direction longitudinally of said body, and including resilient means acting on said compound means to normally hold said respective first valve means closed.

References Cited by the Examiner UNITED STATES PATENTS 2,778,428 1/1957 Baker et al 166-127 2,799,346 7/1957 Baker et al 166-133 2,856,003 10/1958 Fredd 166-224 3,266,576 8/1966 Chenoweth 166--l33 I. A. LEPPINK, Assistant Examiner. CHARLES E. OCONNELL, Primary Examiner. 

1. IN A RETRIEVABLE BRIDGE PLUG, COMPRISING: AN ELONGATED TUBULAR BODY HAVING THEREON WELL WALL ENGAGING PACKER MEANS FOR FORMING A SEAL WITH THE WELL WALL, WELL WALL ENGAGING ANCHOR MEANS OPERABLE FOR ANCHORING SAID BODY TO SAID WELL WALL, WELL WALL ENGAGING FRICTION MEANS FOR EFFECTING OPERATION OF SAID ANCHOR MEANS UPON THE APPLICATION OF PRESSURE DIFFERENTIAL ACROSS SAID PACKER MEANS, SAID BODY HAVING A PASSAGE THERETHROUGH, AN INNER MEMBER EXTENDING LONGITUDINALLY IN SAID PASSAGE AND HAVING MEANS FOR CONTROLLING OPERATION OF SAID ANCHOR MEANS, SAID BODY HAVING A VALVE SEAT, VALVE MEANS CARRIED BY SAID INNER MEMBER CLOSABLE AGAINST SAID SEAT RESPONSIVE TO FLUID PRESSURE TO PREVENT FLOW OF FLUID THROUGH SAID PASSAGE AND OPENABLE UPON MOVEMENT WHEREIN SAID MEMBER IN SAID BODY, THE IMPROVEMENT WHEREIN SAID VALVE MEANS COMPRISES FIRST VALVE MEANS HAVING A SMALL AREA RESPONSIVE TO FLUID PRESSURE HOLDING THE SAME CLOSED AND OPENABLE RESPONSIVE TO INITIAL MOVEMENT OF SAID INNER MEMBER, AND SECOND VALVE MEANS ENGAGEABLE WITH SAID SEAT AND HAVING A LARGER AREA RESPONSIVE TO FLUID PRESSURE HOLDING THE SAME CLOSED AND OPENABLE RESPONSIVE TO FURTHER MOVEMENT OF SAID INNER MEMBER. 